A bomb has killed at least five people and wounded 90 near a Shi'ite procession in Pakistan, police say, as the government struggles to stop a wave of attacks by sectarian Sunni militant groups determined to wipe out the minority sect and seize power.

Sunni hardliners threatened to strike hard this weekend, an important one in the Shi'ite religious calendar, prompting authorities to halt cellphone coverage in several areas to prevent bombings triggered by remote control.

Authorities have also restricted motorcycle travel, hoping to deprive suicide bombers of one mode of transportation.

The wounded from the bombing on Sunday were carried away in the northwestern city of Dera Ismail Khan, where a bomb targeting Shi'ites killed at least seven people, including four children, a day before.

Pakistan's Taliban, who are focused on battling the state but are also allied with Sunni sectarian groups, claimed responsibility for both attacks.

"For Interior Minister of Pakistan Rehman Malik, who blocked mobile phones across the country and banned motorbikes, you can't stop our activities against the Shi'ite community and security forces," Taliban spokesman Ehsanullah Ehasan said by telephone from an undisclosed location.

"We will keep continuing our activities and this is a failure of security forces, police and army that we have made successful attacks in Dera Ismail Khan."

Past attacks during the religious event have killed large numbers of Shi'ites.

Sunday's bomb, planted in a shop near a street market, also wounded five security officials, said senior police official Malik Mushtaq.

Doctors at a hospital in Dera Ismail Khan said five people were killed and 90 wounded. "There is a lack of ambulances and not enough hospital beds," said one. "People brought many of the injured to the hospital on rickshaws."

Hardline Sunni groups, which are becoming increasingly dangerous, have vowed to carry out more attacks as the Shi'ite mourning month of Muharram comes to a climax on Sunday.

Security officials say organisations such as Lashkar-e-Jhangvi (LeJ) are stepping up attacks on Shi'ites, who they regard as non-believers, in a bid to destabilise nuclear-armed, US ally Pakistan and establish a Sunni theocracy.

Al Qaeda, which is close to LeJ, pushed Iraq to the brink of a sectarian civil war several years ago with large-scale suicide bombings of Shi'ites.

More than 300 Shi'ites have been killed in Pakistan so far this year in sectarian conflict, according to human rights groups. The campaign is gathering pace in rural as well as urban areas such as Karachi, Pakistan's biggest city.

Shi'ites account for up to 20 per cent of this nation of 180 million.

The growing death toll has discouraged some Shi'ites from taking part in processions this year during one of their most sacred rituals, when people flagellate themselves with chains and other items to commemorate the martyrdom of the grandson of Islam's prophet, who was killed during the battle of Karbala.

"If I were to compare with last year, the fear has definitely increased," said Sadia Fatema, 28. "Just last night me and my mother were asking my father and brother if they really had to go to the procession. We are worried."

Others say the pressure has made Shi'ites stand up to Sunni hardliners.

"There is fear, but there is also anger and defiance among Shi'ites," said one, who asked not to be named.

"Shi'ites never felt like a minority in Pakistan but now they are slowly being turned into a real minority. And Shi'ites will not let this happen."

Washington, a critical source of financial aid for cash-strapped Pakistan, has been pressuring the South Asian nation to crack down on militants based in tribal areas who cross the border to attack American-led forces in Afghanistan.

Pakistan, meanwhile, faces major domestic security challenges from a wide range of groups, including the Taliban, who capitalise on issues such as unemployment, official corruption and poverty to boost recruitment.

A series of army offensives has failed to break the back of militant groups based along the border with Afghanistan.

"Our children are being killed but the government is powerless," complained Shi'ite Amina Bokhari. "What is the purpose of this security they claim to give us?"